Children with pre- or perinatal unilateral brain injury (PL) exhibit remarkable plasticity for eariy language skills but appear to have difficulty with later developing, more complex aspects of language. This limitation may negatively impact children's school success, which depends not only on basic linguistic skills, but also on the ability to use these skills to link ideas to one another - to make inferences, draw comparisons and analogies, construct hierarchies and partonomies, enlist schemas and definitions - in other words, to use their language skills to engage in higher order thinking. Higher order thinking has been identified as core to children's ability to become adaptive, innovative and academically successful thinkers. Project II examines how children with PL use connected discourse to express higher order thinking from the eariiest stages of language development through eariy adolescence, compared to the SES-matched typically developing children studied in Project I. Project II also examines variations in lesion characteristics and variations in the input parents provide in their talk to illustrate and elicit higher order thinking from their children, with the goal of understanding how biological and input variations relate to the development of children's higher order thinking skills and their academic achievement. By focusing on how language is used for higher order thinking and on academic achievement our research expands what is known about plasticity in this population since existing research has largely focused on early developing language and cognitive skills and has not included information on parental input. The project has three specific aims: (1) Study 1 describes changes in how children with PL develop higher order thinking from 14 months of age through 14 years as a function of their lesion characteristics, and how this development compares to that of typically developing children. (2) Study 2 describes the input the parents of children with PL provide to higher order thinking from 14 to 58 months of age and later at age 10, asking whether there is continuity in this input over time, whether the amount and nature of this input differs as a function of children's lesion characteristics, and whether it differs from the input parents of typically developing children in Project I offer their children. (3) Study 3 asks how the characteristics of children's lesions and the input they receive from parents combine to predict the development of their higher order thinking and their academic achievement, and whether input plays a differentially important role for children with PL compared to TD children. RELEVANCE (See instructions): In the proposed research, we extend work on the role of language input in the development of eariy language functions in children with pre- or perinatal brain injury to an essential aspect of language- the use of language for higher order thinking. It is critical that we identify the kinds of input that support the use of language for higher order thinking in children who are biologically compromised in order to develop interventions that help them develop to their full potential as well as to achieve the broader societal goals of increasing human capital and diversifying the workforce.